Fibrous glass air filter units for use in forced air heating and air conditioning installations have been the subject of many patents. The need for compact, nestable filters has been recognized, see for example Best, U.S. Pat. No. 3,023,839 and Latakas, et al. U.S. Pat. No. 4,105,423. In patent '839, V openings between ends of straight fiberboard side sections are blocked by paper tape, although it is suggested that even without the tape, the openings are blocked to some degree by a bridging portion of a compressed web of fibrous glass. However, when the tape is used, it will interfere with the inward flexing of the side rails of the frame of the filter, and if it is not used, there is bound to be leakage at the corners. Champlin, No. 4,086,071 suggests a construction in which frame members fold inwardly to conserve space. Champlin does suggest the use of tabs 22 to effect interconnection at the comers of the frame. However, when the frame members are folded in, the flaps 22 are disengaged from the adjacent frame member, and must be reengaged when the frame members are erected.
One of the objects of this invention is to provide an air filter with a frame that is flared outwardly from the filter medium, to permit nesting of filters for shipment and storage, with tabs that remain engaged with contiguous frame members.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawings.